Update CMake minimum version

[varunagrawal]

CMake is throwing the warning:

CMake Deprecation Warning at CMakeLists.txt:1 (cmake_minimum_required):
  Compatibility with CMake < 3.5 will be removed from a future version of
  CMake.

  Update the VERSION argument <min> value or use a ...<max> suffix to tell
  CMake that the project does not need compatibility with older versions.

This PR updates all the CMake files to have the minimum version as 3.5 to fix any potential deprecations as well as maintain the largest generality.

[varunagrawal]

Merging